Impact of Carbon Dots on Ionic Conductivity of Isothiocynate-Based Nematic Liquid Crystal

Abstract

The paper report the impact of carbon dots (CDs, diameter ∼2-3 nm) on the ionic conductivity of homogeneously aligned nematic liquid crystal (NLC), namely, 4-(trans-4ʹ-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT), using dielectric spectroscopy. To investigate the effect of frequency, temperature, and dopant (CDs) concentration (0.05, 0.1, 0.2, and 0.5 wt%) on the ionic conductivity of 6CHBT, the loss tangent (tan δ) is measured. For instance, at room temperature, the frequency dependent tan δ clearly shows the significant shift in ionic relaxation peak of 6CHBT toward a higher frequency with increase in dopant concentration. The change in the ionic conductivity with frequency is also observed in all composites. The temperature-dependent studies in temperature range of 28–40 °C clearly show that conductivity increases monotonically with temperature and the change in magnitude is largest for the 0.5 wt% composite. This is attributed to change of homogeneous to homeotropic alignment of NLC due to dopant CDs. To understand more about the significant change in the ionic conductivity, the thermal activation energy is calculated for all composites using an Arrhenius plot. The results are believed to further shed more light on present understanding of dynamics of ionic conduction in pure 6CHBT and its nanocomposites and would be useful for the development of advanced soft composite materials with tunable dielectric properties.